Gas-liquid finned heat exchanger



-. '2 Sheets-Sht 1 F IG. 2

A. HOURWITZ' ETAL GAS-LIQUID FINNED HEAT Excmmefin FIG. 1

Feb. 23,1970

Filed Jan. 2, 1968 INVENTORS AVINOAM HOURWITZ BOLESLAW HOUCHM AN BY fla I ATTORNEY Feb. 3, 1970 A. HOURWITZ ETAL 3,493,041

. GAS-LIQUID FINNED HEATEXCHANGER Filed Jan. 2, 1968 2,Sheets-Sheet 2 FIG. 4

INVENTORS AVINOAM HOURWITZ BOLESLAW-HOUCHMAN United States Patent GAS-LIQUID FINNEDHEAT EXCHANGER Avinoam Hourwitz, 4 Hameassfim St., and Boleslaw Henchman, 11 Hatham Sofer St., both of Tel Aviv,

Israel Filed Jan. 2, 1968, Ser. No. 695,213 Claims priority, application Israel, Jan. 4, 1967,

2 ,21 Int. Cl. rzsr 13/08, 7/10, 1/42 U.S. Cl. 165-147 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The present invention relates to heat exchangers for the exchange of heat between a gas and a liquid.

Description of the prior art In a heat exchanger of the kind specified the rate of heat transfer through the partition between the gas and liquid chambers is proportional to the gas-partition and the partition-liquid heat transfer coefficients and also to the transversal temperature gradient between the chambers. As the partition-liquid heat trans-fer coefficient is higher than the gas-partition heat transfer coefficient, it has already been proposed to increase the efficiency by increasing the gas-partition contact area as compared to the partition-liquid contact area, e.g. by ribbing the par tition on the gas chamber side while keeping it smooth on the liquid chamber side. Thus, heat exchangers are known for the transfer of heat from a donor gas to an acceptor liquid comprising two concentric annular chambers through the inner of which flows the gas and through the outer of which flows the liquid, the surface of the inner chamber for the gas comprising a plurality of longitudinally arranged ribs separated from one another by channels in the form of grooves. The annular gas chamber is formed by the internally ribbed cylinder and an axially extending core, the core and the ribs being substantially coextensive.

It has been found that the above-described heat exchangers suifer from the drawback than no allowance is made for a longitudinal temperature gradient of the gas existing between the intake (hot) and discharge (cold) ends of the gas chamber. It has further been found that the longitudinal temperature gradient may impair the performance of the exchanger in particular when there is a large difference between the temperature of the gas at the hot end and that at the cold end, since the transversal temperature gradient near the cold end may be too low for an efficient heat transfer at this region.

In the known heat exchangers of this type the longitudinal temperature gradient has not been taken into consideration, and it is the object of the present invention to provide an improved heat exchanger of the kind specified with due consideration to this gradient.

SUMMARY OF THE INVENTION The invention provides a gas-liquid heat exchanger adapted for the heat transfer from a gaseous heat donor 3,493,041 Patented Feb. 3, 1970 to a liquid heat acceptor of the foregoing type, i.e., comprising an outer annular liquid chamber and an inner gas chamber separated from each other by a partition of a heat conducting material whose surface on the side of the gas chamber comprises ribs extending in the direction of the gas flow, the outer wall of the gas chamber being defined by the mentioned partition, and the inner wall being defined by a coaxial core, the arrangement being such that the passageway for the gas in the gas chamber being gradually constricted from the hot to the cold end thereof.

By the gradual constriction of the passageway for the gas in the gas chamber the effective contact between the gas and partition increases gradually from hot to the cold end so that the heat transfer efiiciency increases as the temperature of the gas decreases. Also, because of the lower heat transfer efficiency near the hot end the gas gives off less heat in that region than would be the case if the passageway for the gas in the gas chamber were uniform throughout. In consequence, more heat remains available in the gas for transfer near the cold end of the gas chamber with the result that the transversal temperature gradient at this region is higher than would otherwise be the case.

Summing up, in a heat exchanger according to the invention the transversal temperature gradient is decreased near the hot end and increased near the cold end with the result that the overall efficiency of the heat exchanger is increased.

In accordance with one embodiment of the invention the height of the ribs increases gradually from the hot to the cold end of the gas chamber. In this embodiment the shape of the slope of the ridge of each rib will depend on the design and geometry of the exchanger. Thus, the slope may be straight-lined, concave-curved or convex-curved. The gas chamber may be cylindrical and,

if desired, may comprise a substantially cylindrical,

coaxial core defining together with said partition an annular space of uniform width.

In accordance with a second embodiment of the invention the gas chamber is cylindrical and comprises a BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by way of example in the accompanying drawings in which: FIGS. 1, 2 and 4 are axial sections of three heat exchangers according to the invention; and FIGS. 3 and 5 are fragments of sections along lines IIIIII of FIG. 1, and VV of FIG. 4, respectively, drawn to a larger scale.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The heat exchanger illustrated in FIGS. 1 and 3 comprises a cylindrical body 1 and a core 2. An inner tubular partition 3 subdivides the inner space of body 1 into a liquid chamber 4 and a gas chamber 5. The liquid chamber 4 comprises connections 6 and 7, one of which serves as the inlet and the other as the outlet, depending on whether the liquid and gas flow is in counter-current or co-current. Body 1 is fitted with two caps 8 and 9 of which the former serves as the gas inlet and thus constitutes the hot end of the gas chamber, and the latter serves as the gas outlet and thus constitutes the cold end of the gas hamber.

The inner face of partition 3 facing the gas chamber 5 omprises a plurality of ribs 1 the height of each of vhich increases gradually from a minimum near the hot -.nd to a maximum near the cold end of gas chamber 5. t follows from this arrangement that the passageway for he gas in chamber is constricted gradually from the hot 0 the cold end of the chamber. Thus, the effective contact :etween the gas and the partition increases gradually 1 'rom the hot towards the cold end of the chamber, that is, n the same direction as the temperature of the gas lecreases.

The embodiment illustrated in FIG. 2 is basically iimilar to that of FIGS. 1 and 3, except that in FIG. 2 he gradual constriction of the passageway for the gas in :he gas chamber is achieved by a gradual increase of the :ross-sectional area of the core. In this embodiment the ribs a are of uniform height while the diameter of core la is smaller near the hot end of the gas chamber 5 and increases gradually towards the cold end. All other components are identical to those of the embodiment of FIGS. 1 and 3 and are designated by the same numerals. The functioning of this embodiment is similar to that of the embodiment of FIGS. 1 and 3 in that the passageway for the gas chamber 5 is constricted gradually from the hot to the cold end of the chamber, whereby the effective contact between the gas and partition 3 increases gradually in the same direction.

In the embodiment illustrated in FIG. 4 the gas chamber does not include a core, and ribs 10b increase in height gradually from the hot to the cold end so as to meet or nearly meet at a point 11 along the longitudinal axis of the heat exchanger. The remaining components of this exchanger are similar to those of the preceding two embodiments and are therefore indexed by the same numerals. In this embodiment the cylindrical shape of the gas chamber 5 may be modified into a tubular chamber of other cross-sectional shape, e.g. elliptical or polygonal of any kind.

Further variations, applications and embodiments of the invention will be apparent.

What is claimed is:

1. A gas-liquid heat exchanger for the heat transfer from a gaseous heat donor to a liquid heat acceptor, comprising, an outer annular liquid chamber forming a passageway for the liquid, an inner gas chamber forming a passageway for the gas, said chambers being separated from each other by a partition of a heat conducting material whose surface on the side of the gas chamber 0 forms the outer wall of the gas chamber and comprises ribs extending into the passageway for the gas and longitudinally of the gas chamber in the direction of the gas flow, and a coaxial core dis-posed within the gas chamber and forming the inner wall thereof, the passageway for the gas in the gas chamber being gradually constricted from the hot to the cold end thereof, said coaxial core being cylindrical and defining wtih said partition a cylindrical gas chamber, the height of said ribs increasing gradually from the hot to the cold end of the gas chamber.

References Cited UNITED STATES PATENTS 1,307,393 6/1919 Dyer 165--154 1,983,466 12/1934 Kline 165154 2,445,115 7/1948 Hanrahan l147 X 2,740,803 4/1956 Dorschner -147 X FOREIGN PATENTS 1,274,618 9/ 1961 France.

268,479 5/ 1950 Switzerland.

547,263 8/1942 Great Britain.

ROBERT A. OLEARY, Primary Examiner ALBERT W. DAVIS, Assistant Examiner U.S. Cl. X.Ri 

